You could always argue that with Dunn's power Zimmerman was in scoring position at the time. 
regardless, Dunn's numbers with RISP are .267/.433/.644 = OPS: 1.078. In those 45 ABs with RISP he has 5 HRs and 26 RBIs. Just what one would expect from a classic slugger in the cleanup spot.
By comparison, RZ has 44 ABs with RISP and his numbers are .273 .382 .364 OPS = .745. Zimmerman is always looking more for contact. Interesting enough, they both have pretty much the same number of walks and Ks with Dunn obviously having more of each.
with 2 outs and RISP Dunn's OBP is .455 and SLG is .500. Clearly the guy walks alot.